Time for revival of estrogens in the treatment of advanced prostatic carcinoma? Pharmacokinetics, and endocrine and clinical effects, of a parenteral estrogen regimen

BACKGROUND: The present pilot study tested the clinical performance of a new pharmacokinetically guided dosing regimen of parenteral estrogen in patients with advanced prostatic carcinoma. The aim was to accelerate endocrine effects and to avoid cardiovascular side effects. METHODS: Seventeen patients were randomized to intramuscular injections of 240 mg polyestradiol phosphate (PEP) every second week for the first 8 weeks (five doses), followed by a maintenance dose of 240 mg every month; and 16 patients were randomized to bilateral orchidectomy. The estrogen dosing was calculated by pharmacokinetic modelling to achieve a rapid increase in serum estradiol and thereby a fast decrease in testosterone. RESULTS: The predicted increment in serum estrogen was achieved, together with a subsequent decrease in testosterone in the PEP group. In addition, there were no signs of an increased cardiovascular morbidity. This was probably due to a minimal estrogenic influence on the liver and was reflected by unchanged levels of coagulation factor VII. Clinical effects, during the first 2 years of treatment, were similar in the two treatment arms, with 12 patients in the orchidectomy group and 14 patients in the PEP group responding to treatment. CONCLUSIONS: The present parenteral regimen is an efficient and time-saving estrogen regimen with a favorable side-effect profile. PEP seems to offer a potential for revival of the most cost-effective endocrine treatment of cancer of the prostate, i.e., estrogen.